While an aircraft is taxiing at low speed, i.e. other than during stages of takeoff and landing, its braking needs to be managed in such a manner as to take various constraints into account, including passenger comfort.
In order to improve passenger comfort, it is desirable for braking to be both progressive and accurate. Braking that is progressive makes it possible to avoid the passengers feeling decelerations that are too sudden. At low speed, braking that is accurate is important for comfort, since it serves to avoid the pilot being tempted to act repeatedly on the pedals, e.g. while maneuvering the aircraft in response to instructions from a ramp agent and when confronted with residual engine thrust. The state of the art is illustrated in particular by Document FR 2 701 006, which describes a method of controlling an electro-hydraulic brake device in an aircraft wheel set. While the aircraft is taxiing at low speed, that method consists in separately organizing braking for the wheels of first and second distinct groups of braked wheels, using respective relationships for pressure variation that is controlled as a function of the extent to which brake pedals are depressed, each group of wheels having its own function. A first relationship applies over the entire active range of brake pedal depressions, while a second relationship applies only above a certain predetermined depression threshold for said pedals. Use is then made of a number of brakes that increases as a function of the requested level of braking, thus making it possible to ensure that braking is progressive and accurate, and therefore comfortable.
That method presents a certain number of drawbacks. In the event of a brake being unavailable, e.g. when equipment involved in controlling the brake has failed, the effectiveness of the braking that results from the remaining brakes is quite clearly diminished. Furthermore, in the event of one or more brakes presenting temperature or wear greater than the other brakes, the method does not make it possible to reduce that temperature or wear difference.